The present invention is generally directed to toner processes, and more specifically, to aggregation and coalescence processes for the preparation of toner compositions. In embodiments, the present invention is directed to the economical chemical in situ preparation of toners without the need for the use of known toner pulverization and/or classification methods, and wherein in embodiments toner compositions with a volume average diameter of from about 1 to about 25, and preferably from 1 to about 10 microns, and narrow GSD of, for example, from about 1.14 to about 1.26 as measured on the Coulter Counter can be obtained. The resulting toners can be selected for known electrophotographic imaging, printing processes including color processes, digital processes, and lithography.
In reprographic technologies, such as xerographic and ionographic devices, toners with volume average diameter particle sizes of from about 9 microns to about 20 microns are effectively utilized. Moreover, in a number of xerographic technologies, such as the high volume Xerox Corporation 5090 copier-duplicator, high resolution characteristics and low image noise are highly desired, and can be attained by, for example, utilizing the small sized toners of the present invention with, for example, a volume average particle of from about 2 to about 11 microns and preferably less than about 7 microns, and with narrow geometric size distribution (GSD) of from about 1.16 to about 1.3. Additionally, in xerographic systems wherein process color is utilized, such as pictorial color applications, small particle size colored toners, preferably of from about 3 to about 9 microns, are highly desired to avoid paper curling. Paper curling is especially observed in pictorial or process color applications wherein three to four layers of toners are transferred and fused onto paper. During the fusing, moisture is driven off from the paper due to the high fusing temperatures of from about 130.degree. C. to about 160.degree. C. applied to the paper from the fuser. Where only one layer of toner is present, such as in black or in highlight xerographic applications, the amount of moisture driven off during fusing can be reabsorbed proportionally by paper and the resulting print remains relatively flat with minimal curl. In pictorial color process applications wherein three to four colored toner layers are present, a thicker toner plastic level present after the fusing step can inhibit the paper from sufficiently absorbing the moisture lost during the fusing step, and image paper curling results. These and other disadvantages and problems are avoided or minimized with the toners and processes of the present invention.
Also, it is preferable to select for the development of color images toners with small particle sizes, such as from about 1 to 7 microns in volume average diameter, and with higher pigment loading, such as from about 5 to about 12 percent by weight of toner, and such that the mass of toner layers deposited onto a substrate like paper is reduced to enable obtaining excellent image quality, and whereby a thinner plastic toner layer forms on paper after fusing, thereby minimizing or avoiding paper curling. Toners prepared in accordance with the present invention enable in embodiments the use of lower image fusing temperatures, such as from about 120.degree. C. to about 150.degree. C., thereby avoiding or minimizing paper curl. Lower fusing temperatures minimize the loss of moisture from paper, thereby reducing or eliminating paper curl. Furthermore, in process color applications, and especially in pictorial color applications, toner to paper gloss matching is highly desirable. Gloss matching is referred to as matching the gloss of the toner image to the gloss of the paper. For example, when a low gloss image of preferably from about 1 to about 30 gloss is desired, low gloss paper is utilized, such as from about 1 to about 30 gloss units as measured by the Gardner Gloss metering unit, and which after image formation with small particle size toners, preferably of from about 3 to about 5 microns and fixing thereafter, results in a low gloss toner image of from about 1 to about 30 gloss units as measured by the Gardner Gloss metering unit. Alternatively, when higher image gloss is desired, such as from about 30 to about 60 gloss units as measured by the Gardner Gloss metering unit, higher gloss paper is utilized, such as from about 30 to about 60 gloss units, and which after image formation with small particle size toners of the present invention of preferably from about 3 to about 5 microns, and fixing thereafter results in a higher gloss toner image of from about 30 to about 60 gloss units as measured by the Gardner Gloss metering unit. The aforementioned toner to paper matching can be attained with small particle size toners, such as less than about 7 microns and preferably less than about 5 microns, such as from about 1 to about 4 microns, whereby the pile height of the toner layer or layers is considered low and acceptable.